Method of casting an ingot in a thin-walled deformable steel mould

ABSTRACT

A method of manufacturing an ingot made of a high-melting point metal such as iron, steel, nickel, cobalt and alloys thereof, in which a thin-walled mould is vertically and movably supported by a molten bath contained in a bath tank and a molten metal is poured into said mould to move it downwards into said molten bath in response to an increase of the amount of the molten metal poured in the mould. The molten metal poured in the mould is cooled and coagulated upwards in succession from the lower end of the mould, thereby forming an ingot in the mould.

United States Patent Matsunaga et al.

METHOD OF CASTING AN INGOT IN A THIN-WALLED DEFORMABLE STEEL MOULD Inventors: Yonosuke Matsunaga, No. 8, l-chome,

Nishitobe, Nishi-ku, Yokohama Eiichi Kato; Seiji Tobisawa, both of Tokyo, all of Japan Assignee: said Matsunaga, by said Kato and said Tobisawa Filed: Oct. 28, 1969 Appl. No.: 871,908

Foreign Application Priority Data Oct. 28, 1968 Japan ..43/78035 US. Cl ..164/49, l64/7l, 164/128,

164/138 Int. Cl. ..B22d 7/00, B22d 27/02, B22d 27/08 Field of Search ..l64/l22, l28,49,7l, 138

[56] References Cited UNITED STATES PATENTS 1,419,280 6/1922 McNeil] 164/49 2,968,848 1/1961 Carter ..164/128 FOREIGN PATENTS 0R APPLICATIONS 173,082 11/1952 Austria ..l64/49 Primary ExaminerRobert D. Baldwin Attorney-Fleit, Gipple & Jacobson [57] ABSTRACT A method of manufacturing an ingot made of a high-melting point metal such as iron, steel, nickel, cobalt and alloys thereof, in which a thin-walled mould is vertically and movably supported by a molten bath contained in a bath tank and a molten metal is poured into said mould to move it downwards into said molten bath in response to an increase of the amount of the molten metal poured in the mould; The molten metal poured in the mould is cooled and coagulated upwards in succession from the lower end of the mould, thereby forming an ingot in the mould.

4 Claims, 5 Drawing Figures Fig. I

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INVENTORS YONOSUKE MATSUNAGA EIICHI KATO SEIJI TOBISAWA- BY v a J ATTORNEYS 1 i METHOD OF CASTING AN INGOT IN A THlN-WALLED DEFORMABLE STEEL MOULD This invention relates to methods of manufacturing ingots made of a high melting point metal such as iron, steel, nickel, cobalt and alloys thereof.

l-leretofore, in case of manufacturing an ingot use has been made of a thick-walled mould whose thickness is sufficient to absorb heat generated from a molten metal poured into the mould and prevent the mould wall from being deformed by the pressure subjected to it during pouring of the metal therein. In general, the above-mentioned thick-walled mould made of cast iron and adapted to manufacture an iron ingot, steel ingot etc., must have such a large thickness that the weight of the mould becomes 1.5 to 2.5 times that of the ingot and that the mould as a whole must be homogeneous in order to make the strength of the mould uniform, with the result that the mould not only becomes expensive, but also becomes short in life and hence is not economical. Particularly, the mould for use in manufacturing a billet or plate made of a high melting point metal and alloy thereof is limited in dimension and must have a larger weight ratio between the mound and the ingot in order to prevent deformation of the mould. Moreover, the life of such mould is shorter than that of a common mould for manufacturing an ingot and becomes tall in height so that operations become difficult and the cost of manufacturing the ingot becomes higher.

In the well-known method heretofore proposed of manufacturing the ingot by using the above-mentioned thick-walledtype mould capable of absorbing the heat generated by the molten metal poured there in and supporting the weight of the molten metal by the thick wall has the disadvantage that degassing becomes incomplete and dendritic structure and segregation occur.

The principal object of the invention is to obviate the above-mentioned disadvantages in a manner such that a molten metal is poured into a thin-walled mould which is then caused to be moved downwards into a molten bath, that heat generated from the molten metal is transmitted through the mould wall to the molten bath to cool the molten metal, that the pressure of the molten bath is applied to the mould wall to prevent it from being deformed by the molten metal poured into the mould, that the molten metal is cooled in succession from the lower end of the mould to effect degaseous action in an extremely easy manner and prevent occurrence of the segregation, thereby obtaining an ingot having a superior quality.

A feature of the invention is the provision s such an improved method of manufacturing an ingot comprising vertically and movably supporting a thin-walled mould with its open end directed upwards upon a molten bath acting as agent for cooling a molten metahpouring said molten metal into said mould to move said mould downwards in response to the increase of the amount of said molten metal poured in said mould and cool and coagulate said molten metal poured in said mould upwards in succession from the lower end of said mould, and removing an ingot thus produced from said mould.

In a preferred embodiment of the invention, provision is made of a dish-shaped thin-walled mould having a height appropriately proportioned to the thickness of an ingot to be manufactured and the mould is made floated upon and supported by the molten bath.

In another preferred embodiment of the invention, the thinwalled mould is made of a nonmagnetic stainless alloy or stainless steel and surrounded by an electric coil and the molten metal during its pouring and coagulation in the mould is subjected to a magnetic field produced from the current flowing through the electric coil, whereby to'produce a magnetically anisotropic ingot.

In further I preferred embodiment of the invention, ultrasonic oscillation is applied to the thin-walled mould during coagulation of the molten metal poured into he thin-walled mould, whereby to effect degassing from the molten metal and make crystal particles of the ingot extremely minute.

The invention makes it possible to adopt various means of giving a sufficient buoyancy to the mould even after it has been moved downwards into the molten bath. V

In case of using the dish-shaped thin-walled mould the suffrcient buoyancy of the mould can easily be obtained by making the height of the mould larger then any desired thickness of the ingot to be manufactured. Thus, molten salts or molten slag having a relatively low specific gravity and adapted to be commonly used in the well-known salt bath furnace may be used as the molten bath. In case of using such salt bath or molten slag as the molten bath a buoyancy which is sufficient to cause the mould to float upon the molten bath can be given to the mould after the molten metal has been poured therein. Thus, it is preferable to make the height of the mould higher then the thickness of the ingot.

The height h of the mould is given by the following formula h=plT+pll +a where p is a specific gravity of the molten bath, p a specific gravity of the molten metal, T a thickness of the ingot to be manufactured, p" a specific gravity of the material constituting the mould, t a thickness of the mould and a an extra height to be determined by taking the sidewall portion of the mould and a desired height of that portion of the floating mould which projects above the molten bath into consideration.

Other objects and features will appear in the following specification, reference being had to the drawing, in which:

FIG. 1 is a longitudinal sectional view of an apparatus for carrying out the method according to the invention into effect, a mould being shown in a state before a molten metal is not yet poured therein;

FIG. 2 is the same view as FIG. 1, a mould being shown in another state after the molten metal has been poured therein;

FIG. 3 is a longitudinal sectional view of a modified apparatus for carrying out the method according to the invention into efi'ect;

FIG. 4 is a longitudinal sectional view of another modified apparatus for carrying out the method according to the invention into effect, a mould being shown in a state before a molten metal is not yet poured therein; and

FIG. 5 is the same view as FIG. 4, the mould being shown in another state after the molten metal has been poured therein.

Referring first to FIGS. 1 and 2, there are shown the most simplified apparatus for carrying out the method according to the invention into effect in which 1 designates a bath tank, 2 a molten bath such as lead bath enclosed in the bath tank 1, 3 a cooling pipe adapted to control the temperature rise of the molten bath 2 to any desired value and hence maintain the molten bath 2 at constant temperature, 4 a heat-insulating material covering the surface of the molten bath 2 for the purpose of preventing the molten bath 2 such as lead bath from becoming oxidized or preventing the other kind of molten bath 2 from becoming excessively cooled by atmosphere. As the molten bath 2, lead and alloys thereof which melt at a relatively low temperature and metal salts having a high specific gravity may be used.

In the invention provision is made of a mould 5 open at one end and made of stainless steel such as AISl 304, 3l6, 309, 310 or Cr-Mo alloy steel. The thickness of the mould 5 is appropriately proportioned to any desired size of the ingot, but is made considerably thin if compared with that of a conventional mould.

the thin wall of the mould 5 to the molten bath 2 surrounding the mould 5 and absorbed by the molten bath 2, with the result that the molten metal 6 poured in the mould 5 is cooled and hence coagulated in a manner progressing in succession upwards from the lower end of the mould 5. If the amount of the molten metal 6 poured into the mould 5 is increased, the total weight of the mould 5 is increased and the mould 5 is caused to be moved further downwards into the molten bath 2. Thus that part of the mould 5 which contains the molten metal 6 therein is supported by the pressure of the molten bath 2 surrounding the mould 5 to prevent deformation of the thin wall of the mould 5. At the same time the molten metal 6 poured into the mould 5 is effectively cooled and coagulated upwards in succession by means of the molten bath 2 surrounding the mould 5. In the embodiment shown the difference in the specific gravities between the molten metal 6 and the molten bath 2 permits of always producing in the mould 5 a high-temperature hot top portion 7 covering the top surface of the molten metal 6. Thus, in practice it is preferable to make the specific gravity of the molten bath 2 higher than that of the molten metal 6.

FIG. 3 shows a modified apparatus for carrying out the method according to the invention into effect. In the present embodiment, the upper opening of the bath tank 1 is closed by a cover plate 8 which is provided at its center with a guide hole 9 through which is vertically extended through the mould 5 whose lower end is immersed into the molten bath 2.

The apparatus constructed as described above confines vapor generated from the molten bath 2 in a space formed above the molten bath 2 to maintain a vapor pressure in this space. Alternatively, air, an inert gas or nonoxidizing gas may be introduced under pressure from the outside into the closed space above the molten bath 2 to apply the pressure P against the top surface of the molten bath 2 and hence form a desired hot top portion 7 on the molten metal 6 poured into the mould 5 FIGS. 4 and 5 show another modified apparatus for carrying out the method according to the invention into effect, wherein provision is made of a dish-shaped mould 5 to manufacture an ingot for use in manufacturing metal plates.

In the present embodiment, a suitable well-known salt bath 2 which has commonly been used in salt bath furnace is used as the molten bath 2. The dish-shaped mould 5 is made of stainless steel such as A181 304, 316, 309, 310 or Cr-Mo alloy steel. The height of the dish-shaped mould 5 is appropriately proportioned to any This thickness of the ingot and determined to about three times higher than the thickness of the ingot to be obtained. The dish-shaped mould 5 thus constructed floats on the molten bath 2.

The molten bath 2 is maintained at a temperature of 400 C,, for example, and a molten metal 6 of stainless steel maintained at a temperature of l,600 C., for example, is poured into the mould 5. This pouring of the molten metal 6 causes the dish-shaped mould 5 to move downwards into the molten bath 2. The heat radiated from the molten metal 6 is transmitted through the thin wall of the dish-shaped mould 5 to the molten bath 2 surrounding the dish-shaped mould 5 and absorbed by the molten bath 2 with the result that the molten metal 6 poured into the dish-shaped mould 5 is cooled and hence coagulated in a manner progressing in succession upwards form the lower end of the dish-shaped mould 5. If the amount of the molten metal 6 is increased, the total weight of the dish-shaped mould 5 is increased and the dish-shaped mould 5 is caused to be moved further downwards into the molten bath 2. Thus, that part of the dish-shaped mould 5 which contains the molten metal 6 therein is supported by the pressure of the molten bath 2 surrounding the dish-shaped mould 5 to prevent deformation of the thin wall of the dishshaped mould 5. At the same time the molten metal 6 poured into the dish-shaped mould 5 is effectively cooled and coagulated upwards in succession by means of the molten bath 2 surrounding the dish-shaped mould 5.

As explained hereinbefore the use of the flat dish-shaped mould 5 described insures flotation and support of the dishshaped mould 5 on the molten bath 2 without necessitating any special supporting means and further provides the important advantage that the molten metal 6 poured into the dishshaped mould 5 can be cooled upwards in succession from the lower end of the dish'shaped mould 5 and that impurities and particularly gas etc., occluded in the molten metal 6 can easily be removed from the wide surface of the molten metal 6, thereby obtaining an ingot having a superior quality.

In the method according to the invention described above, the molten bath 2 absorbs the heat generated from the molten metal 6 poured into the mould 5 and hence the temperature of the molten bath 2 becomes slightly raised. This temperature rise of the molten bath 2 can be compensated, if necessary, by circulating a cooling water through the cooling pipe 3. Thus, the temperature of the molten bath 2 can easily be maintained at a constant value within a suitable temperature range such as 400 to 600 C. Thus, it is possible to produce isothermal transformation whereby effecting so-called austempering. As a result of this, the advantage is obtained that the coagulated metal after being removed from the mould 5 can be subjected to a surface treatment only so as to form an ingot having a property suitable for rolling etc., or an ingot for use in manufacturing metal plates.

In case of pouring the molten metal, if necessary, flux, heatinsulating material or deoxidizing agent may be added in the mould 5 in the well-known manner.

The dish-shaped mould 5 may also be applied to manufacture an ingot for use in forming metal bars. In such a case the dish-shaped mould 5 may be provided therein with a plurality of longitudinally or transversely extending partition walls so as to divide the inside of the dish-shaped mould 5 into a plurality of elongate chambers.

Molten bath of lead or other low melting point metals or alloys thereof or molten bath of slag, salts etc., having a relatively high specific gravity may be used as the cooling agent. The cooling agent may be used in the form of two layers. In this case if a molten bath of a metal having a good heat conductivity and alloy thereof is used as the lower layer the cooling effect can be increased, while if a molten bath of salts or a slag is used as the upper layer the cooling effect from the top surface of the molten bath can be reduced.

Salts etc., may be introduced into he mould 5 preparatory to the pouring of the molten metal 6 therein. Such salts etc., can prevent wear of the mould 5 and improve the surface of the ingot.

The description and examples given above are intended to illustrate the best mode of performing our invention. It is apparent that many modifications thereof may occur to those skilled in the art, which will fall within the scope of the following claims.

We claim:

1. A method for manufacturing an ingot comprising l supporting a thin-walled steel mould having an open end vertically and movably upon a cooling bath so that the open end of the mould is directed upward, said mould and said cooling bath associating to result in sufficient buoyancy so that when molten metal is poured into the mould the mould submerges into the cooling bath in proportion to the increase in height of the metal poured into the mould; (2) pouring molten metal into the mould so that the mould submerges into the cooling bath in proportion to the increase in height of the metal poured into the mould; (3) allowing the molten metal in the mould to cool and solidify upwards in succession from the lower end of said mould, and (4) removing an ingot thus produced from the mould, said process being further characterized in that the walls of said mould are so thin that the mould is deformable when filled with molten metal and that the walls of the mould are subjected to sufficiently high external pressure by the cooling bath to substantially counteract the hydrostatic pressure of the molten metal thus preventing deformation of the mould.

stainless alloy steel or steel and is subjected to a magnetic field to produce a magnetically anisotropic ingot. a

4. A method of manufacturing an ingot as claimed in claim 1 comprising further subjecting ultrasonic oscillations to said thin-walled mould during coagulation of said molten metal poured into said thin-walled mould. 

1. A method for manufacturing an ingot comprising (1) supporting a thin-walled steel mould having an open end vertically and movably upon a cooling bath so that the open end of the mould is directed upward, said mould and said cooling bath associating to result in sufficient buoyancy so that when molten metal is poured into the mould the mould submerges into the cooling bath in proportion to the increase in height of the metal poured into the mould; (2) pouring molten metal into the mould so that the mould submerges into the cooling bath in proportion to the increase in height of the metal poured into the mould; (3) allowing the molten metal in the mould to cool and solidify upwards in succession from the lower end of said mould, and (4) removing an ingot thus produced from the mould, said process being further characterized in that the walls of said mould are so thin that the mould is deformable when filled with molten metal and that the walls of the mould are subjected to sufficiently high external pressure by the cooling bath to substantially counteract the hydrostatic pressure of the molten metal thus preventing deformation of the mould.
 2. A method of manufacturing an ingot as claimed in claim 5, in which provision is made of a dish-shaped thin-walled mould having a height appropriately proportioned to the the thickness of an ingot to be manufactured and the mould is made floated upon and supported by the molten bath.
 3. A method of manufacturing an ingot as claimed in claim 1, in which said thin-walled mould is made of a nonmagnetic stainless alloy steel or steel and is subjected to a magnetic field to produce a magnetically anisotropic ingot.
 4. A method of manufacturing an ingot as claimed in claim 1 comprising further subjecting ultrasonic oscillations to said thin-walled mould during coagulation of said molten metal poured into said thin-walled mould. 